Compilare: main.cpp: In function 'void df(int, int)': main.cpp:23:5: warning: unused variable 'i' [-Wunused-variable] int i; ^ main.cpp: In function 'int main()': main.cpp:34:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("amici2.in","r",stdin); ^ main.cpp:35:37: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("amici2.out","w",stdout); ^ main.cpp:36:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&t); ^ main.cpp:38:26: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] { scanf("%d%d",&n,&m); ^ main.cpp:42:28: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&x,&y); ^